Apparatus for laterally correcting the position of the blue beam in a crt

ABSTRACT

A plurality of magnetic rubber disks each axially magnetized to form a first magnet in a first portion and a second magnet in a second portion diametrically opposed to the first portion and with the poles positioned oppositely. The disks are axially aligned on a common spindle, with adjacent poles being similar, and the spindle is rotatably mounted adjacent the neck of a multi-beam cathode ray tube. The magnetized disks are mounted to produce variable amounts of movement, in either direction, of the blue beam while producing lateral movement of the other two beams in the opposite direction.

United States Patent 91 Lostumo Jan. 23, 1973 [75] Inventor:

Ill.

[73] Assignee: Motorola, Inc., Franklin Park, Ill.

[22] Filed: 7 Jan. 14, 1972 [21] Appl. No.: 217,807

[52] U.S. Cl ..335/2l2, 313/77 [51] Int. Cl ..H0lt1/00 [58] Field of Search ..3l3/77; 335/210, 212

[56] References Cited UNITED STATES PATENTS 3,308,328 3/1967 Rennick ..3l3/77 3,512,023 5/1970 Anthony ..3l3/77 Arthur J. Lostumo, Franklin Park,

12/1971 Anthony ..335/2l2 Primary ExaminerGeorge Harris Attorney-Vincent Rauner et al.

571 ABSTRACT A plurality of magnetic rubber disks each axially magnetized to form a first magnet in a first portion and a second magnet in a second portion diametrically opposed to the first portion and with the poles positioned oppositely. The disks are axially aligned on a common spindle, with adjacent poles being similar, and the spindle is rotatably mounted adjacent the neck of a multi-beam cathode ray tube. The magnetized disks are mounted to produce variable amounts of movement, in either direction, of the blue beam while producing lateral movement of the other two beams in the opposite direction.

6 Claims, 5 Drawing Figures APPARATUS FOR LATERALLY CORRECTING THE POSITION OF THE BLUE BEAM IN A CRT BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is especially useful in threegun cathode ray tubes utilized in color television and the like. Three-gun cathode ray tubes utilize a shadow or aperture mask spaced from the screen and it is desirable to have the beams produced by the three guns i converge at the mask so that they will pass through the openings of the mask and impinge upon the triad of color dots behind each opening. In conventional static convergence apparatus, three radially spaced apart magnets are utilized to adjust the position of the beams in a radial direction. However, because of physical and electrical variations in the cathode ray tubes and in the convergence apparatus, a simple radial displacement of the beams may not produce convergence at the desired point. Thus, it is necessary to include apparatus for producing a lateral movement of the beams.

It has been found that two of the beams can be substantially converged with radial movements and complete convergence can be attained by lateral movement of the beam from the upper gun, arbitrarily designated the blue gun. Because a magnetic field which will produce lateral movement of the blue beam will adversely affect the other two beams, special magnetic apparatus has be designed to produce a field which laterally moves the blue beam while producing no resultant movement of the other two beams or producing a slight lateral movement of the other two beams in the opposite direction. 2. Description of the Prior Art In the prior art a plurality of ferrite rods, each having a circular cross section, are magnetized diametrically. The rods are coaxially aligned with adjacent poles alternating in polarity and the entire assembly is mounted adjacent the neck of a three-gun CRT so that the axis of the rods is perpendicular to the axis of the CRT. By utilizing an odd number of poles along the rod assembly and mounting the central pole directly above the blue beam, a magnetic field is formed which moves the blue beam laterally in either direction and the other two beams laterally in the opposite direction. However, the

' ferrite rods are relatively expensive and it is extremely difficult to mount the rods (or rod if the assembly is constructed as an integral unit) tov prevent axial movement thereof. Since movement of the beams is affected by lines of magnetic flux cutting the beams and since the direction of movement of the beam is directly dependent upon the direction of the lines of flux, it can be seen that any axial movement of the magnet assembly will place each of the beams in a different portion of the magnetic field and substantially alter the direction of the lines of flux relative to the three beams.

SUMMARY OF THE INVENTION thereto on the disk. A magnetic field is produced in the neck of the cathode ray tube which causes the one beam to move laterally an amount and in a direction dependent upon the rotary position of the disk assembly and the remaining two beams are caused to move laterally in the opposite direction. The disks are coaxially affixed to an elongated spindle and mounted on a frame having spacers between the disks which substantially prevent axial movement thereof while allowing rotary movement.

It is an object of the present invention to provide an improved apparatus for affecting lateral movement of a single beam in a multi-beam cathode ray tube.

It is a further object of the present invention to provide apparatus for affecting lateral movement of a single beam in a multi-beam cathode ray tube, which apparatus is relatively inexpensive and simple to construct.

It is a further object of the present invention to provide apparatus for affecting lateral movement of a beam in a multi-beam cathode ray tube, which apparatus is mounted to substantially prevent axial movement thereof.

These and other objects of this invention will become apparent to those skilled in the art upon consideration of the accompanying specification, claims and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Referring to the drawings, wherein like characters indicate like parts throughout the figures:

FIG. 1 is an axial sectional view of a cathode ray tube. with one embodiment of the present invention mounted thereon;

FIG. 2 is a view in top plan of the apparatus illustrated in FIG. 1;

FIG. 3 is a view in side elevation of the apparatus illustrated in FIG. 1;

FIG. 4 illustrates schematically the apparatus of FIG. 1 with the approximate resultant field of the magnets illustrated in broken lines; and

FIG. 5 is an enlarged exploded view in perspective of a portion of the apparatus illustrated in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the figures, the numeral 10 generally designates a mounting base formed of nonmagnetic material, such as plastic or the like. In the present embodiment the mounting base 10 is also a mounting base for the convergence unit affecting radial movement of the beams of a cathode ray tube, but it should be understood that the present apparatus could be mounted on a separate base if desired. The mounting base 10 encircles the neck of a multi-gun cathode ray tube 11. Three radially outwardly extending arms are formed as an integral part of the mounting base 10 and define a mounting base for three magnets affecting radial convergence of the three beams. Each of the three arms is radially aligned with one of the beams of the cathode ray tube 11, one arm extending generally vertically upwardly so as to be radially aligned with the upper or blue beam of the cathode ray tube 11. The present lateral convergence apparatus, generally designated 15, is affixed to the upwardly extending arm of the mounting base 10, generally above the neck of the cathode ray tube 1 1.

Five fingers 20-24 are formed as an integral part of the mounting base so as to extend outwardly from the upper arm of the mounting base 10 generally parallel with the axis of the cathode ray tube 11 and in a common plane. The outwardly extending end of each of the fingers -24 has a longitudinally extending slot therein adapted to receive an axle 25. The fingers 20-24 are positioned in spaced apart relationship with the central finger 22 disposed approximately radially above the upper or blue beam and the fingers 20, 21 and 23, 24 spaced symmetrically on either side thereof.

Four disks 30, 31, 32 and 33 are formed of magnetizable material. In the present embodiment the disks 30-33 are formed of a powdered magnetic material and a synthetic rubber or plastic binder. This material was selected because it is relatively inexpensive and easy to work with, however, it should be understood that other materials might be utilized if desired. Each of the magnetic disks 30-33 is magnetized axially to form a first magnet in a first portion thereof and a second magnet in a second portion diametrically opposed to the first portion. The poles of the two magnets in each of the disks 30-33 are oriented oppositely so that each major surface of each of the disks 30-33 has a north and a south pole of each of the magnets in the disk positioned in diametrically opposed portions thereof. In addition, each of the disks 30-33 has a mounting opening coaxially formed therethrough. In the present embodiment the opening through the disks is generally hexagonal shaped to fixedly position the disks 30-33 on the axle 25 for rotation therewith and to correctly orient each of the disks -33 on the axle 25 relative to each of the other disks. The axle 25 is formed with four raised portions 35, having a hexagonal shaped cross section, spaced apart along the length thereof. Further, five portions 36 having a somewhat smaller diameter are formed on each side of the hexagonal portions to be received within the slot in the ends of the fingers 20-24. The portions of the axle 25 on either side of the portions 36, having a somewhat larger diameter, form shoulders to engage the sides of the fingers 20-24 and prevent axial movement ofthe axle 25 while allowing rotary movement thereof. The magnetized disks 30-33 are press fit onto the hexagonal portions 35 of the axle 25. The portions 36 of the axle 25 are engaged in the slots of the fingers 20-24 so that the disk 30 is positioned between the fingers 20-21, the disk 31 is positioned between the fingers 21-22, the disk 32 is positioned between the fingers 22-23, and the disk 33 is positioned between the fingers 23-24. One outermost end of axle 25 has a cylindrical knob affixed thereto for manual rotation of the axle 25 and the disks 30-33 affixed thereto.

Each of the disks 30-33 is affixed to the axle 25 so that adjacent poles are similar, as can be seen in FIG. 4. With the disks 30-33 positioned as described above and the axle 25 rotated as shown in FIG. 4, the net magnetic field is substantially as illustrated in FIG. 4 and lines of flux cut the upper beam, designated 41, generally vertically to produce lateral movement thereof (indicated by the arrow) while lines of flux cut the other two beams, designated 42 and 43, generally vertically but in the opposite direction to produce lateral movement thereof (indicated by the arrows) in the opposite direction. Rotation of the axle 25 changes the amount or direction of the lines of flux cutting the beams 41, 42 and 43 but does not substantially 'alter the field so that only the amount or direction of the lateral movement is changed.

Thus, improved apparatus for laterally converging multiple beams of a cathode ray tube is disclosed. In the disclosed apparatus improved magnets are utilized which are relatively inexpensive and simple to work with and improved mounting structure is disclosed for substantially preventing axial movement of the assembly while allowing rotary movement thereof. While a specific embodiment for the axle 25 is illustrated and disclosed, which embodiment prevents axial movement by engaging the sides of the fingers 20-24, it should be understood that the fingers 20-24 might be constructed sufficiently wide to engage the sides of the disks 30-33 directly to prevent axial movement and the axle 25 could be constructed with a single continuous outer diameter. The disks 30-33 could be press fit or otherwise fixedly attached to the axle 25 for rotation therewith.

While I have shown and described a specific embodiment of this invention, further modifications and improvements will occur to those skilled in the art. I desire it to be understood, therefore, that this invention is not limited to the particular form shown and I intend in the appended claims to cover all modifications which do not depart from the spirit or scope of this invention.

Iclaim:

l. Converging apparatus, for a cathode ray tube having a plurality of electron beams, comprising:

a. a plurality of disks of magnetic material each magnetized axially in a first portion thereof to form a first magnet and magnetized axially in a second diametrically opposed portion to form a second magnet with the poles oriented opposite the poles of the first magnet;

. means mounting said disks in axial alignment and axially spaced apart with adjacent poles on adjacentdisks being similar and fixed relative to each other for common rotary movement; and

. means further mounting said disks with the axes thereof generally perpendicular to the axis of the cathode ray tube and oriented relative to the tube for affecting a lateral movement of one of said beams without adversely affecting the remaining beams and mounting said disks for rotation about the axes thereof for varying the amount and direction of lateral movement of said one beam.

2. Converging apparatus as set forth in claim 1 wherein four disks are positioned symmetrically about a line mutually perpendicular to the axes of the disks and the axis of the cathode ray tube.

3. Converging apparatus as set forth in claim 1 wherein the disks are constructed of a material including a plastic binder.

4. Converging apparatus as set forth in claim 1 wherein themeans mounting the disks includes an elongated axle with each of the disks fixedly attached thereto for rotation therewith.

5. Converging apparatus as set forth in claim 1 wherein the means further mounting the disks includes nonmagnetic material forming a base with a plurality of integrally attaches spacers positioned between adjacent disks for preventing axial movement of said disks.

6. Converging apparatus as set forth in claim 5 wherein the base is formed integrally with a radial convergence unit. 5 

1. Converging apparatus, for a cathode ray tube having a plurality of electron beams, comprising: a. a plurality of disks of magnetic material each magnetized axially in a first portion thereof to form a first magnet and magnetized axially in a second diametrically opposed portion to form a second magnet with the poles oriented opposite the poles of the first magnet; b. means mounting said disks in axial alignment and axially spaced apart with adjacent poles on adjacent disks being similar and fixed relative to each other for common rotary movement; and c. means further mounting said disks with the axes thereof generally perpendicular to the axis of the cathode ray tube and oriented relative to the tube for affecting a lateral movement of one of said beams without adversely affecting the remaining beams and mounting said disks for rotation about the axes thereof for varying the amount and direction of lateral movement of said one beam.
 2. Converging apparatus as set forth in claim 1 wherein four disks are positioned symmetrically about a line mutually perpendicular to the axes of the disks and the axis of the cathode ray tube.
 3. Converging apparatus as set forth in claim 1 wherein the disks are constructed of a material including a plastic binder.
 4. Converging apparatus as set forth in claim 1 wherein the means mounting the disks includes an elongated axle with each of the disks fixedly attached thereto for rotation therewith.
 5. Converging apparatus as set forth in claim 1 wherein the means further mounting the disks includes nonmagnetic material forming a base with a plurality of integrally attaches spacers positioned between adjacent disks for preventing axial movement of said disks.
 6. Converging apparatus as set forth in claim 5 wherein the base is formed integrally with a radial convergence unit. 